A man fatally shot in a Hamilton house overnight was lying in bed and died protecting his partner in the gunfire, his family says.

Robert Nelson, 23, is believed to have died at the scene of a shooting at 4 Matthews Cres, Melville about 1am this morning.

His 20-year-old partner Kahlee and a 17-year-old man, believed to be a family friend, were also seriously injured.

The two injured victims were taken to Waikato Hospital.

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This morning a hospital spokesperson said the woman was in a serious condition in the High Dependency Unit, while the teenager was critical in the Intensive Care Unit.

The shooter is still at large.

Nelson's family is stunned by the murder.

His sister Erin said they believed the attack was random or a case of mistaken identity by a gang. She stressed her brother was an "innocent person caught in the crossfire".

"Somebody arrived to the house and attacked about four people inside. There was another person holed up inside who wasn't injured," she said.

Her brother had died "covering his girlfriend" from the bullets, Erin said.

She was "absolutely gutted" and described her brother as her "best friend" and a "fun, happy guy" with a "bright future".

"He was a year older than me. His name was Robert and I am Erin so we were Burt and Ernie you know. It is absolutely gutting for us," she said.

"He had such a bright future. He was a chef and just getting his apprenticeship sorted out and about to move on to real nice restaurant soon.

"He will be remembered as the fun, happy guy. He always had a smile on his face and a little sparkle in his eye. He was the life of the party and has been taken so savagely."

Erin Nelson said the two injured victims had severe injuries and were in intensive care. One of them had gone through surgery.

She believed the two victims had also been shot.

Robert Nelson also had a younger brother and two half siblings.

"The family loves him and the world lost a really great person. He has touched a lot of people's lives and they are now going to be missing such a bright person," Erin Nelson said.

"We have a really good network down here so we will be fine, and he was part of one of the biggest hospitality groups in Hamilton which he was quite a big part of, so we will have a lot of support."

A neighbour on Matthews Cres said she slept right through the incident but knew the family who lived at the address.

"They are fabulous neighbours. I am quite upset about it," she said.

"They were really kind and nice to me.

"They never have parties so I don't know what the hell is going on."

The neigbour said there were two armed offenders squad members guarding the property.

A scene examination will commence today, with scientists from the Institute of Environmental Science and Research (ESR) called in.

Anyone with information relating to the incident is asked to contact the investigation team at the Hamilton Police Station, or Crimestoppers anonymously on 0800 555 111.